#8 Habitat Selection II

Habitat requirement

A habitat attribute (not a habitat!) necessary for an individual to survive and reproduce

• Non-negotiable must for the animal to use that habitat

What are some examples of Habitat requirement?

• Amphibians and MANY others–> need standing water

  • Has to be there at some part→ can’t complete a part of their lifecycle 

• Wood Ducks→ nesting cavities

Critical habitat

A habitat necessary for a species or population to survive and/or reproduce

Why is critical habitat an identified area that is really important for a species to survive/reproduce?

• Insulated from threats

• Not something ecological

  • Something that is protected by the ESA

• more of a legal rather than environmental designation

What are some categories within habitats?

• Habitat use

• Habitat availability

• Habitat selection

Habitat use

occupation of habitat in space and time (no implication of choice)

Habitat availability

the area (proportion or acreage) of habitats from which an organism may select

Habitat selection

process by which an organism uses one habitat over another; comparing use and availability leads to inferences about selection

• Use of something by a species in one area over another 

  • Relative to the availability of resources

Habitat selection at the Broadest scale selects for what?

• Climate/temperature

• Terrain

• Historical occupancy

  • Across a huge area

• Evolutionary history

• Species distribution

Habitat selection at the Regional scale selects for what?

• A little more specific but still has to do with a large amount of populations 

• Climate/temperature

• Dominant vegetation and structure

• Hydrology

• Broad resources

• Individual/population home range

  • Migratory routes

Habitat selection at the Local scale selects for what?

• Specific resources

  • Food vs nesting sites vs refuges 

• Often transitory

• Species or populations’ “foraging habitat” or other specific use

  • Accessing different life cycle stages at this scale

Habitat selection at the Microhabitat scale selects for what?

• MANY different reasons, often unknown and of interest!

• Specific items in the foraging area

• Why do the plant/animal occur over here and not anywhere else

What is the orders of habitat selection?

• Animals have to make decisions from a broad-> narrow scale

  • Ex: i want to live on this continent, in this half, at this spot

How do animals decide which habitat to select?

• Factors influencing habitat selection

  • Extrinsic vs. intrinsic factors

  • Proximate cues vs. ultimate causes (result of the decision)

How can selection can be innate, learned, or both?

Some cases– innate

• selection for certain characteristics appears “hard-coded” and inflexible

Some cases– learned 

• selection is affected by prior experience and learning

Extrinsic factors

Characteristics related to habitat itself that result in selection for or avoidance of that habitat

• More intuitive to us of what makes a habitat more attractive to an animal to select

What are some Extrinsic factors that influence habitat selection?

• Predator presence 

• Food abundance

• Density of conspecifics 

  • Availability of mates

• Water 

What are some Density conspecifics that are extrinsic?

• Competition

• Facilitation

• Mating opportunities

Selection coefficient

The degree to which environmental conditions in a wetland influence the survival and reproduction of different species or genotypes

• (e.g., flooding, salinity, nutrient availability, oxygen levels)

What does Selection coefficient look for?

What variables are specific for habitat selection

• Put together a ton of extrinsic variables into a graph and see how they all relate and what is more significant

What does it mean if the Selection coefficient is positive, neutral, or negative?

• pos-> animal selects for something

• neutral-> animal are not selecting for or against it

• neg-> they are not selecting it

Intrinsic factors

• the state of individuals or groups that may influence where they are found

• State of the animal and the state of the habitat

What are the first 4 examples of Intrinsic factors?

• Species

  • EX: mice might select for risk/food differently than a bison will

• Sex

• Age

  • How old/experienced you are

• Body size/condition

  • Select for better spots if you are better at fighting off others

How are different sexes examples of Intrinsic factors?

• Reproductive status

• Differences in care

  • Female might select habitat to nest where its best to raise young

• Different nutritional needs

• Where they can be found, or not, by mates

What are the last 4 examples of Intrinsic factors?

• Proximate “state”

• Subspecies/population

• Behavioral phenotype

• Experience/familiarity

How is Proximate “state” an example of Intrinsic factors?

• If you are starving, you may take a risk at predation to get food

• If you have better health, you might pick habitat that is a lot more safe

What are the 2 causes of habitat selection

• Ultimate

• Proximate

Proximate causes of habitat selection

The cues that animals use to select habitats; behavioral mechanisms for habitat selection

• Sensory stimuli, memories, others that suggest an animal to pick that area

• Cognitive response

Ultimate causes of habitat selection

The fitness consequences of habitat selection or avoidance; those conferring survival or reproductive value

• Increased/decreased survival

• Increased/decreased reproduction

Proximate cues of selection

immediate, observable environmental features that organisms use to decide where to settle, forage, or reproduce

• A response to a specific influence or cue, usually with connoted consequences to fitness and ultimate outcomes

What are some Proximate cues of selection examples?

• Specific vegetation

• Basic stimulus such as color or reflectivity

• Sensory input

  • EX: color

• Signs of prey

• Presence of conspecifics

What is Tinbergen’s theory of “summation of stimuli”?

• the sum of all stimuli/cues in a habitat must meet a minimum threshold for an individual to select it or to remain… 

  • a reasonable theory or a ‘just so story?’

    • Something we accept => it makes intuitive sense to us

      • Need to back it up with evidence

What happens if you have pos proximate cues?

•  Will want to respond to that area

• If you have two pos proximate cue

  • the response will be stronger

• More pos proximate cues with higher response

  • some mental math is happening

How do animals evaluate and weigh proximate cues?

Not going to be one specific thing that an animal uses to pick a habitat

• EX: Are you going to a patch that has mates, but might mean you will be in more competition with other males

  • Are you going to an area with better resources, with tracks from a predator relating to that predator being in the area

Optimality theory

• Optimal foraging, diet, mate choice, habitat selection, many more

  • Maximizing benefits and minimizing costs

    • Animals are seen as making “decisions” by weighing costs and benefits.

    • The chosen habitat is–in theory–the one that maximizes fitness payoff (benefits/opportunities–costs/risks).